.TH std::regex_match 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::regex_match \- std::regex_match

.SH Synopsis
   Defined in header <regex>
   template< class BidirIt,

             class Alloc, class CharT, class Traits >
   bool regex_match( BidirIt first, BidirIt last,
                     std::match_results<BidirIt, Alloc>& m,           \fB(1)\fP \fI(since C++11)\fP
                     const std::basic_regex<CharT, Traits>& e,
                     std::regex_constants::match_flag_type flags =

                         std::regex_constants::match_default );
   template< class BidirIt,

             class CharT, class Traits >
   bool regex_match( BidirIt first, BidirIt last,                     \fB(2)\fP \fI(since C++11)\fP
                     const std::basic_regex<CharT, Traits>& e,
                     std::regex_constants::match_flag_type flags =

                         std::regex_constants::match_default );
   template< class CharT, class Alloc, class Traits >

   bool regex_match( const CharT* str,
                     std::match_results<const CharT*, Alloc>& m,      \fB(3)\fP \fI(since C++11)\fP
                     const std::basic_regex<CharT, Traits>& e,
                     std::regex_constants::match_flag_type flags =

                         std::regex_constants::match_default );
   template< class STraits, class SAlloc,

             class Alloc, class CharT, class Traits >
   bool regex_match( const std::basic_string<CharT, STraits, SAlloc>&
   s,
                     std::match_results<
                         typename std::basic_string<CharT, STraits,   \fB(4)\fP \fI(since C++11)\fP
   SAlloc>::
                             const_iterator,
                         Alloc>& m,
                     const std::basic_regex<CharT, Traits>& e,
                     std::regex_constants::match_flag_type flags =

                         std::regex_constants::match_default );
   template< class CharT, class Traits >

   bool regex_match( const CharT* str,
                     const std::basic_regex<CharT, Traits>& e,        \fB(5)\fP \fI(since C++11)\fP
                     std::regex_constants::match_flag_type flags =

                         std::regex_constants::match_default );
   template< class STraits, class SAlloc,

             class CharT, class Traits >
   bool regex_match( const std::basic_string<CharT, STraits, SAlloc>&
   s,                                                                 \fB(6)\fP \fI(since C++11)\fP
                     const std::basic_regex<CharT, Traits>& e,
                     std::regex_constants::match_flag_type flags =

                         std::regex_constants::match_default );
   template< class STraits, class SAlloc,

             class Alloc, class CharT, class Traits >
   bool regex_match( const std::basic_string<CharT, STraits,
   SAlloc>&&,
                     std::match_results<
                         typename std::basic_string<CharT, STraits,
   SAlloc>::                                                          \fB(7)\fP \fI(since C++11)\fP
                             const_iterator,
                         Alloc>&,
                     const std::basic_regex<CharT, Traits>&,
                     std::regex_constants::match_flag_type flags =

                         std::regex_constants::match_default ) =
   delete;

   Determines if the regular expression e matches the entire target character sequence,
   which may be specified as std::string, a C-string, or an iterator pair.

   1) Determines if there is a match between the regular expression e and the entire
   target character sequence [first, last), taking into account the effect of flags.
   When determining if there is a match, only potential matches that match the entire
   character sequence are considered. Match results are returned in m.
   2) Behaves as \fB(1)\fP above, omitting the match results.
   3) Returns std::regex_match(str, str + std::char_traits<CharT>::length(str), m, e,
   flags).
   4) Returns std::regex_match(s.begin(), s.end(), m, e, flags).
   5) Returns std::regex_match(str, str + std::char_traits<CharT>::length(str), e,
   flags).
   6) Returns std::regex_match(s.begin(), s.end(), e, flags).
   7) The overload \fB(4)\fP is prohibited from accepting temporary strings, otherwise this
   function populates match_results m with string iterators that become invalid
   immediately.

   Note that regex_match will only successfully match a regular expression to an entire
   character sequence, whereas std::regex_search will successfully match subsequences.

.SH Parameters

   first, last - the target character range to apply the regex to, given as iterators
   m           - the match results
   str         - the target string, given as a null-terminated C-style string
   s           - the target string, given as a std::basic_string
   e           - the regular expression
   flags       - flags used to determine how the match will be performed
.SH Type requirements
   -
   BidirIt must meet the requirements of LegacyBidirectionalIterator.

.SH Return value

   Returns true if a match exists, false otherwise. In either case, the object m is
   updated, as follows:

   If the match does not exist:

   m.ready() == true
   m.empty() == true
   m.size() == 0

   If the match exists:

   m.ready()          true
   m.empty()          false
   m.size()           number of marked subexpressions plus 1, that is, 1 +
                      e.mark_count()
   m.prefix().first   first
   m.prefix().second  first
   m.prefix().matched false (the match prefix is empty)
   m.suffix().first   last
   m.suffix().second  last
   m.suffix().matched false (the match suffix is empty)
   m[0].first         first
   m[0].second        last
   m[0].matched       true (the entire sequence is matched)
   m[n].first         the start of the sequence that matched marked sub-expression n,
                      or last if the subexpression did not participate in the match
   m[n].second        the end of the sequence that matched marked sub-expression n, or
                      last if the subexpression did not participate in the match
   m[n].matched       true if sub-expression n participated in the match, false
                      otherwise

.SH Notes

   Because regex_match only considers full matches, the same regex may give different
   matches between regex_match and std::regex_search:

 std::regex re("Get|GetValue");
 std::cmatch m;
 std::regex_search("GetValue", m, re);  // returns true, and m[0] contains "Get"
 std::regex_match ("GetValue", m, re);  // returns true, and m[0] contains "GetValue"
 std::regex_search("GetValues", m, re); // returns true, and m[0] contains "Get"
 std::regex_match ("GetValues", m, re); // returns false

.SH Example


// Run this code

 #include <cstddef>
 #include <iostream>
 #include <regex>
 #include <string>

 int main()
 {
     // Simple regular expression matching
     const std::string fnames[] = {"foo.txt", "bar.txt", "baz.dat", "zoidberg"};
     const std::regex txt_regex("[a-z]+\\\\.txt");

     for (const auto& fname : fnames)
         std::cout << fname << ": " << std::regex_match(fname, txt_regex) << '\\n';

     // Extraction of a sub-match
     const std::regex base_regex("([a-z]+)\\\\.txt");
     std::smatch base_match;

     for (const auto& fname : fnames)
         if (std::regex_match(fname, base_match, base_regex))
             // The first sub_match is the whole string; the next
             // sub_match is the first parenthesized expression.
             if (base_match.size() == 2)
             {
                 std::ssub_match base_sub_match = base_match[1];
                 std::string base = base_sub_match.str();
                 std::cout << fname << " has a base of " << base << '\\n';
             }

     // Extraction of several sub-matches
     const std::regex pieces_regex("([a-z]+)\\\\.([a-z]+)");
     std::smatch pieces_match;

     for (const auto& fname : fnames)
         if (std::regex_match(fname, pieces_match, pieces_regex))
         {
             std::cout << fname << '\\n';
             for (std::size_t i = 0; i < pieces_match.size(); ++i)
             {
                 std::ssub_match sub_match = pieces_match[i];
                 std::string piece = sub_match.str();
                 std::cout << "  submatch " << i << ": " << piece << '\\n';
             }
         }
 }

.SH Output:

 foo.txt: 1
 bar.txt: 1
 baz.dat: 0
 zoidberg: 0
 foo.txt has a base of foo
 bar.txt has a base of bar
 foo.txt
   submatch 0: foo.txt
   submatch 1: foo
   submatch 2: txt
 bar.txt
   submatch 0: bar.txt
   submatch 1: bar
   submatch 2: txt
 baz.dat
   submatch 0: baz.dat
   submatch 1: baz
   submatch 2: dat

   Defect reports

   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.

      DR    Applied to           Behavior as published              Correct behavior
                       basic_string rvalues were accepted, which rejected via a deleted
   LWG 2329 C++11      was likely to result in dangling          overload
                       iterators

.SH See also

   basic_regex   regular expression object
   \fI(C++11)\fP       \fI(class template)\fP
   match_results identifies one regular expression match, including all sub-expression
   \fI(C++11)\fP       matches
                 \fI(class template)\fP
   regex_search  attempts to match a regular expression to any part of a character
   \fI(C++11)\fP       sequence
                 \fI(function template)\fP
